Scanned light beam imaging is employed for various purposes including electrophotographic printing. In such systems used for printing, a light beam generated, for example, by a laser is selectively modulated to vary its amplitude while it is scanned laterally across a moving photoconductor to selectively discharge the photoconductor. Such systems have been binary in nature (xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d) to accomplish printing of character information by selectively either exposing the photoconductor or leaving it unexposed. To insure complete exposure, adjacent scan lines are usually overlapped slightly. Thus, any slight misalignment of the scans or change in beam size would not be noticed.
This cannot be done if the light beam modulation is other than binary because in any partial exposure, a substantial overlap would appear as a stripe of complete exposure. Alternatively, spacing the scans apart would appear as a stripe that remains unexposed. To attempt to prevent such stripes by substantially eliminating the optical and mechanical tolerances from the system would appear to be prohibitively expensive.
It is therefore an object of the present invention to eliminate the perception of elongated stripes in such optical imaging systems without requiring substantial tightening of allowable optical or electro-mechanical tolerances.
A method for banding suppression due to vibration in an image forming and/or image receiving apparatus with laser driver utilizes governing equations which relate the on/off time and intensity to velocity and frequency of vibration are disclosed. Using derived formulas, an amplitude and frequency modulation (AM/FM) combination is used to suppress the banding due to vibration. The equation which governs the on/off time (FM) is t1+e sin(2xcfx80ft1)/vn=t0. This transcendental equation can be solved for the required on-time t1 in terms of the nominal on-time t0, e (vibration amplitude), v0 (nominal velocity) and f (vibration frequency). The equation which governs the intensity is H3(t)=v(t)/v0. H3(t) controls the level of irradiance. This method is further extended to multi-temporal vibration frequency and may correct banding due to irradiance modulation.